After more than a dozen consumers in Michigan reported tasting something more in their bottles of Pepsi than they bargained for, the state’s health department issued a warning that customers should return certain 16-ounce bottle of the soda that may contain flakes of metal.

MLive reports that the Michigan Department of Agriculture and Rural Development issued a consumer advisory warning residents of the state to discard select 16.9-ounce bottles of Pepsi after tests found they contained metal flakes.

An investigation by the Department, initiated after receiving a customer complaint, found that an unspecified number of bottles contained small flecks — between 0.1 millimeters and 0.3 millimeters — of iron and chromium.

The metal flecks likely entered the bottles due to a malformation on the bottling line.

Affected products were sold at select Michigan retailers this spring. They can be identified by the product codes HC022373 and HC022473. The bottle should be returned to the stores where they were purchased for a refund.

Pepsi says it is aware of 18 instances in which customers complained of a metallic taste while drinking the beverage.

MLive notes that Pepsi previously removed bottles of Pepsi from 200 Michigan stores. However, the Department of Agriculture believes some of the affected product could have been purchased before they were removed.